Auto-tumor killer cells in the lymphocyte population of patients with solid tumors will be generated using two procedures, by exposure to allogeneic lymphocytes in a nonspecific way, and by exposure to autologous and allogeneic tumor cells, in a specific way. The resulting cytotoxicities will be analysed for overlapping killer subsets in cold target competition experiments and by that establish whether cross reactivities exist. The effect of IFN on the function of lymphocytes isolated from the biopsy specimen will be tested. IFN enhances the cytotoxic potential of freshly isolated blood lymphocytes. A proportion of the tumor infiltrating lymphocytes have been shown to have features in common with activated cells, suggesting that they may be in a physiological state that is refractory to IFN activation.